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From "ihawk ihawker" <>
Subject Modeling heterogeneous entities (inheritance issue)
Date Thu, 10 Jul 2008 14:38:01 GMT
Thank you for the answer. As I understand I follow Composition  Design, but
still have problems with implementing inheritance...

It seems my first message was badly formatted.
So I'll copy it in this message again:


I am trying to model a list of heterogeneous entities by having a
ListItem table where the  list item entity is able to point to an
arbitrary entity (Person, Computer, URL, Movie, etc).

I don't want to use single-table inheritance natively supported by
Cayenne because of big database size overheads (the entities are
drastically different from one another).  In fact I don't necessarily
want to use inheritance at all (PersonListItem, ComputerListItem,
etc), but this seems to be the only option in Cayenne to model such a

I've read Mike Kienenberger's article
( about
simulation of vertical inheritance in Cayenne and found that it might
be acceptable for my case.

But I am having problems generating classes from the velocity template
 given in the article, although I've used code generator parameters
recommended in article.

It seems the parser fails to parse ${objEntity.getClientSuperClassName()},
${anObjEntity.getClientClassName()}, although other methods/attributes
of "objEntity", "entityUtils", "stringUtils", "importUtils" are parsed

I've tried with Cayenne 2.0.4, Cayenne 3.0M4.

Thank you,

Andrey Strib.

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